The developer solution for developing colour photographic materials, in particular for developing colour photographic paper, is prepared from or, in the case of continuous operation, replenished with concentrates which contain the necessary constituents.
It is conventional to provide three different concentrates, as certain constituents of the developer bath are not mutually compatible on extended storage. Thus, for example, one concentrate contains the antioxidant, an auxiliary solvent and an optical brightener, a second concentrate contains the colour developer substance, for example 4-(N-ethyl-N-2-methylsulfonylaminoethyl)-2-methylphenylenediamine sesquisulfate (CD-3) or 4-(N-ethyl-N-2-hydroxyethyl)-2-methylphenylenediamine sulfate (CD-4) and a third concentrate contains the buffer substance, alkali and a water softener.
There has been no lack of attempts to develop stable, one-part colour developer concentrates as handling errors during preparation or replenishing of a developer solution may consequently be avoided.
The following one-part concentrates are currently commercially available, a) Monoline(copyright) RA-4 CD-R from Tetenal, a two-phase concentrate with a solid, undissolved phase deposited at the bottom and b) TriPhase(copyright) RA-4 CD-R from Trebla, a three-phase concentrate with undissolved constituents in the middle phase (c.f. also U.S. Pat. No. 5,891,609).
In both cases, the presence of undissolved constituents is disadvantageous for the purposes of handling the concentrate. Especially when preparing the regenerating solution, problems may occur because the undissolved constituents dissolve only poorly. It is also disadvantageous to use one-part concentrates which, while initially containing no undissolved constituents, have a tendency at low temperatures, for example during storage or transport at down to xe2x88x927xc2x0 C., to form precipitates which are insoluble or only sparingly soluble when the temperature is raised.
A one-part, one-phase concentrate known as Prime SP, which has a very high solvent content and is suitable only for certain regeneration rates, is also commercially available from Kodak.
JP published patent application 10 333 302 discloses a one-part colour developer concentrate which contains the least possible sulfate and is stable and in one phase due to addition of triethanolamine and establishing a pH of 12.8 or higher. It is only suitable for low regeneration rates of for example 70 mL/m2, as are used in developing machines operating at full capacity utilisation.
EP 980 024 (published on 16.02.2000) and U.S. Pat. No. 6,017,687 (published on 25.01.2000) describe homogenous, one-part, low-sulfate colour developer concentrates.
U.S. Pat. No. 5,914,221 describes a one-part colour developer concentrate comprising a concentrated suspension of a liquid phase and a non-homogeneous solid phase.
However, if higher regeneration rates of approx. 120 mL/m2 or even 160 mL/m2 are to be used, i.e. if the concentrates are to be more highly diluted, as is the case in developing machines operating at lower capacity utilisation or susceptible to oxidation and/or evaporation or for professional use, it is not possible to use such alkaline concentrates. However, if the pH value in this concentrate is reduced, the colour developer substance begins to precipitate.
The object of the invention was to provide a one-part concentrate for a colour developer which contains no undissolved constituents, which, when cooled to temperatures of down to xe2x88x927xc2x0 C., does not form precipitates which are insoluble or only sparingly soluble when the temperature is raised and from which regeneration solutions may be prepared for any desired regeneration rate.
This object is achieved by producing a multi-phase, in particular two-phase concentrate which, apart from the conventional chemicals required for developing a colour photographic material, contains at most 0.1 mol of sulfate ions/L. The colour developer substance is, for example, added to the concentrate not as the sulfate, as is usual with CD-3 or CD-4, but instead as a phosphate, p-toluenesulfonate, chloride or as the free base.
CD-3 (sesquisulfate) or CD-4 (sulfate) may also be used and the sulfate ions removed by precipitation with metal ions and filtration.
In a preferred embodiment, the concentrate furthermore contains a minimum quantity of one or more water-soluble organic solvents.
In a preferred embodiment, the organic solvent contains a mixture of polyethylene glycols of differing molecular weights from monoethylene glycol up to polyethylene glycol having an average molecular weight of 20000, for example a mixture of diethylene glycol, polyethylene glycol having an average molecular weight of 400 and polyethylene glycol having an average molecular weight of 1500. The average molecular weights are weight averages.
In this manner, it is possible to establish optimum conditions for non-precipitating, one-part developer concentrates.
The polyethylene glycol mixture in particular constitutes at least 90 vol. % of the organic solvent.
A concentrate for the purposes of the invention is an aqueous preparation, 1 part by volume of which is diluted with 1 to 39 parts by volume of water in order to produce a ready-to-use solution; the concentrate contains at least 50 mmol, preferably 70 to 700 mmol of colour developer substance/L.
The present invention accordingly provides a one-part colour developer concentrate which does not precipitate during storage and contains at least one colour developer substance, at least one antioxidant, at least one water softener, a buffer system, alkali and contains at most 0.1, preferably at most 0.05 and particularly preferably at most 0.02 mol of sulfate ions/L, characterised in that the concentrate is a multi-phase, in particular two-phase, concentrate.
Water-soluble organic solvents which may be considered are those from the range of glycols, polyglycols, alkanolamines, aliphatic and heterocyclic carbonamides, aliphatic and cyclic monoalcohols, wherein 50 to 95 wt. %, preferably 60 to 90 wt. % of the total of water and water-soluble solvent is water.
Suitable water-soluble solvents are, for example, carboxylic acid amide and urea derivatives such as dimethylformamide, methylacetamide, dimethylacetamide, N,Nxe2x80x2-dimethylurea, tetramethylurea, methanesulfonamide, dimethylethyleneurea, N-acetylglycine, N-valeramide, isovaleramide, N-butyramide, N,N-dimethylbutyr-amide, N-(2-hydroxyphenyl)acetamide, N-(2-methoxyphenyl)acetamide, 2-pyrrolidinone, xcex5-caprolactam, acetanilide, benzamide, toluenesulfonamide, phthalimide;
aliphatic and cyclic alcohols, for example isopropanol, tert.-butyl alcohol, cyclohexanol, cyclohexanemethanol, 1,4-cyclohexanedimethanol;
aliphatic and cyclic polyalcohols, for example glycols, polyglycols, polywaxes, trimethyl-1,6-hexanediol, glycerol, 1,1,1-trimethylolpropane, pentaerythritol, sorbitol;
aliphatic and cyclic ketones, for example acetone, ethyl methyl ketone, diethyl ketone, tert.-butyl methyl ketone, diisobutyl ketone, acetylacetone, acetonylacetone, cyclopentanone, acetophenol;
aliphatic and cyclic carboxylic acid esters, for example trimethoxymethane, methyl acetate, allyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol diacetate, glycerol 1-acetate, glycerol diacetate, methylcyclohexyl acetate, methyl salicylate, phenyl salicylate;
aliphatic and cyclic phosphonic acid esters, for example methylphosphonic acid dimethyl ester, allylphosphonic acid diethyl ester;
aliphatic and cyclic oxyalcohols, for example 4-hydroxy-4-methyl-2-pentanone, salicylaldehyde;
aliphatic and cyclic aldehydes, for example acetaldehyde, propanal, trimethylacetaldehyde, crotonaldehyde, glutaraldehyde, 1,2,5,6-tetrahydrobenzaldehyde, benzaldehyde, benzenepropane, terephthalaldehyde;
aliphatic and cyclic oximes, for example butanone oxime, cyclohexanone oxime;
aliphatic and cyclic amines (primary, secondary or tertiary), for example ethylamine, diethylamine, triethylamine, dipropylamine, pyrrolidine, morpholine, 2-aminopyrimidine;
aliphatic and cyclic polyamines (primary, secondary or tertiary), for example ethylenedi amine, 1-amino-2-diethylaminoethane, methyl-bis(2-methylaminoethyl)-amine, permethyldiethylenetriamine, 1,4-cyclohexanediamine, 1,4-benzenediamine;
aliphatic and cyclic hydroxyamines, for example ethanolamine, 2-methylethylamine, 2-methylaminoethanol, 2-(dimethylamino)ethanol, 2-(2-dimethylaminoethoxy)-ethanol, diethanolamine, N-methyldiethanolamine, triethanolamine, 2-(2-amino-ethylamino)ethanol, triisopropanolamine, 2-amino-2-hydroxymethyl-1,3-propanediol, 1-piperidineethanol, 2-aminophenol, barbituric acid, 2-(4-aminophenoxy)-ethanol, 5-amino-1-naphthol.
Processing conditions, suitable colour developer substances, suitable buffer substances, suitable water softeners, suitable optical brighteners, auxiliary developers, wetting agents, development accelerators and antifogging agents are described on pages 102 to 107 of Research Disclosure 37 038 (February 1995).
Multi-phase means that the concentrate contains two or more liquid phases, but no precipitation. The liquid phases are, for example, an aqueous and an organic phase.
Suitable antioxidants are compounds of the formulae (I), (II) and (III). 
in which
R1 means optionally substituted alkyl,
R2 means optionally substituted alkyl or optionally substituted aryl and
n means 0 or 1
preferably those in which at least one of the residues R1 and R2 contains at least onexe2x80x94OH, xe2x80x94COOH or xe2x80x94SO3H group; 
xe2x80x83in which
R3 means an optionally substituted alkyl or optionally substituted acyl group; 
xe2x80x83in which
R4 means an alkylene group optionally interrupted by O atoms and
m means a number of at least 2.
The alkyl groups R1, R2, R3, the alkylene group R4 and the aryl group R2 may bear further substituents in addition to the stated substitution.
Examples of suitable antioxidants are 
The phase boundary disappears on dilution of the concentrate with water to produce the ready-to-use colour developer or regenerator; the ready-to-use developer is one-phase.